Ukraine borders the Black Sea on the north. Russia borders that body of water on the east. The Crimean peninsula extends from Ukraine into the Black Sea. Last month, after the collapse of Ukraine's pro-Russia government, Russian troops moved into Crimea. Soon after that, Russia annexed the region — over the protests of Ukraine, the U.S. and many Western nations.

As we reported earlier today, pro-Russia gunmen continue to occupy many government buildings in eastern Ukraine — despite warnings from the Ukrainian government that it will use force, if necessary, to remove them. With tens of thousands of his troops just across the border, there are fears that Russian President Vladimir Putin may send troops into eastern Ukraine.

On Monday, Ukrainian President Oleksandr Turchynov has asked U.N. Secretary-General Ban Ki-moon to send international peacekeepers into eastern Ukraine with Ukrainian troops.